The present invention relates to an apparatus for separating blank pistachio shells from intact pistachio nuts.
Pistachio nuts have a hard shell around the edible kernel and a pericarp or hull which encases the shell. It is necessary to mechanically hull pistachios in order to process commercial quantities of the nut. Ripe pistachios shells are split prior to processing and the nut within the shell may be lost during processing, resulting in a number of blank shells. Pistachios which are not fully ripe may be closed. Many closed shell pistachios have an incompletely formed kernel inside, referred to as xe2x80x9cblanksxe2x80x9d. Some pistachios in which the shell has split early may have been damaged by exposure to the elements, fungal contamination or by insect damage. Furthermore, twigs, branches and other debris may be included with the pistachios.
It is a laborious job to manually remove the blank shells, blanks, damaged pistachios and other unwanted debris from the good pistachio nuts. Therefore, there is a need in the art for an automated process and system for separating and removing blank pistachio shells, blanks, damagaed pistachios and other debris during the processing of pistachio nuts.
In general term, the invention provides a method and apparatus for separating and removing blank pistachio shells, blanks, damaged pistachios and other debris. The pistachios are deposited in a flotation tank filled with water to a controlled level. A weir skims the surface of the water and gathers objects which are floating. The weir leads to a discharge channel. At least one pair of counter-rotating rollers are approximately level with the weir and the water surface. The rollers squeeze the floating objects and urge them towards the weir. Blank pistachio shells, blanks, damaged pistachios and other debris tend to float. Good pistachios tend to sink and deposit on the bottom of the flotation tank. A conveyor or equivalent means removes the good pistachios from the tank for further processing. Some good pistachios float as a result of air bubbles trapped within the pistachio shell. The squeezing action of the rollers tends to free the air bubbles, causing such good pistachios to sink.
Therefore, in one aspect, the invention comprises an apparatus for separating floating items from good pistachio nuts comprising:
(a) a flotation tank having an inclined bottom;
(b) a conveyor disposed along the inclined bottom of the flotation tank for removing pistachio nuts from the bottom of the flotation tank;
(c) a weir and discharge channel for skimming and removing floating items from the surface of water held in the flotation tank; and
(d) at least one pair of counter-rotating horizontal rollers associated with the tank, wherein an upper roller is disposed above a lower roller and an interface between the upper and lower rollers is substantially level with the weir.
In another aspect, the invention may comprise an apparatus for separating good pistachio nuts from floating items comprising:
(a) a flotation tank;
(b) a weir and discharge channel for skimming floating debris from the flotation tank;
(c) roller means for squeezing floating items and urging floating items towards the weir and discharge channel; and
(d) means for removing good pistachio nuts from the bottom of the flotation tank.
In another aspect, the invention may comprise a method of separating pistachio nuts from floating items comprising the steps of:
(a) providing a flotation tank filled with water;
(b) providing a weir and discharge channel for skimming floating items from the flotation tank;
(c) squeezing floating items between two counter-rotating rollers; and
(d) collecting pistachio nuts from the bottom of the flotation tank.